Solar System Log by Andrew Wilson, published 1987 by Jane's Publishing Co. Ltd.

Identical to Mariner 6, Mariner 7 had a similar mission of flying by Mars. After Mariner 6 had returned intriguing photos of Mars's south polar cap, controllers reprogrammed Mariner 7's control system to increase the number of scans of the south pole from 25 to 33.

Following a perfect midcourse correction on the way to Mars on 8 April 1969, on 30 July 1969, just 7 hours before Mariner 6 was scheduled to fly by Mars, the deep space tracking station at Johannesburg, South Africa, lost contact with the spacecraft's high-gain antenna. One of two stations in Madrid, Spain, was diverted from its original mission of tracking Pioneer 8 and joined the search for Mariner 7. Fortunately, the Pioneer station at Goldstone in California's Mojave Desert picked up faint signals from the spacecraft. Controllers sent commands to Mariner 7 to switch to the low-gain antenna, which worked well afterwards.

Despite problems with positional calibration, Mariner 7 recorded 93 far-encounter and 33 near-encounter images of the planet, showing heavily cratered terrain very similar to images recorded by Mariner 6. The closest approach to Mars was at 05:00:49 UT on 5 August 1969, at a distance of 3,430 kilometers. Oddly, despite the high resolution of 300 meters, Mariner 7 found the center of Hellas to be devoid of craters.

The spacecraft found a pressure of 3.5 millibars and a temperature of -90°F at 59° south latitude and 28° east longitude in the Hellespontus region, suggesting that this area was elevated about 6 kilometers above the average terrain. One photo from Mariner 7 showed the moon Phobos. Although surface features were not visible, the picture clearly showed the moon to be irregularly shaped.

Key Dates

27 Mar 1969: Launch (22:22:01 UT)

5 Aug 1969: Mars Flyby (05:00:49 UT)

Status: Successful

Fast Facts

Mariners 6 and 7 were twin spacecraft.

Together they took close up photographs of about 20 percent of the Martian surface.

Mariner 7 found Mars' moon Phobos was irregularly-shaped.

People Spotlight

Ellis Miner"The amazement is in recognizing that by exploring space we are doing something that's never been done before. I never tire of talking about it."